Many fluid processes are known for mixing material with gases. These include also versions employing jet streams, such as, for example, the method of employing a jet stream ejected from a nozzle (U.S. Pat. Nos. 2,786,280, and 2,786,281). In this process, there is supplied pressurized air to a granular material disposed in a container through a nozzle pointing in a vertical direction, the jet stream opening up a channel in an axial direction of the granular material layer. This channel behaves operatively as a pneumatic conveyor, through which the jet stream ejected from the nozzle conveys a portion of the material in an upwardly direction. The granular material arriving in this fashion at the surface of the material layer then slides downwardly along the walls of the container, is then returned to the vicinity of the nozzle, and thus participates in a continuous jet-like movement of the material.
In the interest of a reliable implementation of the channel being formed along the axis of the material layer, it is known to often use a tube at this location, to aid in the formation of the channel, which tube cooperates with the nozzle arranged therebelow in a way similar to an injector, and participates in the transport of the material as a conveying tube, using a dense supply stream. (Scientific results of the technical-chemical Research Institute of the Hungarian Academy of Sciences III Veszprem, 1975, p. 173.)
The container of an apparatus forming a jet stream may be implemented in different versions, either according to the above-described patent, or according to other references or sources; the supply of raw materials to the system, and the discharge of the materials can be accomplished by different methods and at different locations (Dr. L. Imre, Handbook Relating to Drying, paragraphs 15.2.3). There is also known the series-and parallel-switching of a plurality of devices used in jet streams. (Hungarian Pat. No. 160,333.1).
A common disadvantage of the above-described arrangement is the fact that the dimensions, and consequently also the efficiency or output of devices of the above-described kind provided with nozzles is limited, and that therefore the energy requirement or demand of the air blower is high, in view of the high pressure required for setting in motion the needed jet stream. In known devices employing jet streams, the operative pressure of the compressed air, or of the drying medium, is greater than the hydrostatic pressure of the material layer subjected to the jet treatment. A further important factor, which limits the applicability of the method of applying the jet stream, is the fact that in a device using nozzles of the aforesaid type, whether they are used in conjunction with the tube or without the tube, only materials having grains of limited size can be processed, and of these only those which have suitable properties, to ensure that the grains of the material may roll with respect to one another. In the case of angular or cornered grains, adhering relatively strongly to one another, a continuous jet movement cannot take place, but instead there occur discontinuous impacts, formation of craters in the material, a generation of a subsidiary jet system, or swelling of the grains.
To obviate the disadvantageous properties of the jet stream method, namely, the limited dimensions of the device, the relatively large energy requirement for ventilation, the failure to realize a jet movement in the event of materials not complying with the requirement for grains to be capable of rolling with respect to one another, and the required maximum dimensions of the grains, there has been used an apparatus employing jet streams, making use of a plurality of nozzles, so that both the dimensions and the output of the device could be increased to a considerable measure. (Palaine, Nemeth, Raticz, Ratkai: New Construction for Jet-Like Devices, 2d. edition of the Conference of Construction of Chemical Machines, Budapest, January, 1975). The treatment by means of a jet stream of grains not meeting the grain rolling requirements, and the prescribed or limiting dimensions of the grains cannot, however, be administered to such grains by this means, and neither can the energy requirement for ventilation be produced thereby. The latter objectives can be obtained by a method employing jets implemented by an auxiliary air stream, where a portion of the fluid or gas is introduced, not by means of a nozzle, but through a gas-permeable floor disposed below the materials to be dried. The required gas pressure is, however, very considerable, also in this case.